1. Field of the Invention
The present invention relates to a projection system in which a large image is projected and displayed using a combination of a plurality of devices, a control method for the projection system, and a projection apparatus.
2. Description of the Related Art
Conventionally, a projector that projects an image generated by a light valve such as a liquid crystal panel onto a screen is known as a projection apparatus. Since the distance between the projector and the screen is generally arbitrary, the projector needs a function of focusing on the screen at arbitrary distances.
Methods for focusing include a manual focusing method and an automatic focusing method. In the manual focusing method, while looking at a projected image on the screen, a user manually adjusts a focus adjustment mechanism provided in a projection optical system, and sets the mechanism at the position where sharpness of the image on the screen is high. This method imposes a heavy burden on the user.
Japanese Patent Laid-Open No. 2004-274354 discloses an automatic focusing method. Specifically, the focal length is changed while projecting an image onto a screen from a projector, and the image projected during that change period is captured to thereby detect the focal length to the center of an image projection region. Then, a projection optical system is controlled so as to have the detected focal length. Normally, the center portion of an image is considered to be the most important, and thus it is often desirable to focus in the center of a projection picture plane.
Further, Japanese Patent Laid-Open No. 2008-061160 discloses multi-projection that realizes projection of a large picture plane using a plurality of projectors.
For example, in multi-projection in which two projectors are horizontally arranged, and the projectors are respectively caused to project a right half and a left half of one picture plane, the horizontal length of a picture plane can be increased two-fold by horizontally arranging the projected images on a screen. FIG. 2 shows examples of projection picture planes. Reference numeral 200 denotes a screen serving as a projection plane. Reference numeral 201 denotes a projection picture plane projected by a first projector (not shown). Reference numeral 202 denotes a projection picture plane projected by a second projector (not shown). In FIG. 2, the two projection picture planes 201 and 202 constitute a single multi-projection picture plane.
The conventional projectors focus at the center position of the respective projected images. Accordingly, in the example shown in FIG. 2, the projector that projects the projection picture plane 201 focuses at a center position 203 of the projection picture plane 201, in the case of using the autofocus method. Similarly, the projector that projects the projection picture plane 202 focuses at a center position 204 of the projection picture plane 202, in the case of using the autofocus method.
However, in multi-projection, a single picture plane is constituted by a plurality of projected images, and it is preferable to focus at a center position 205 of the entire picture plane.